Protective shield



May 2, 1%67 N. REINHARDT 3,317,723

PROTECTIVE SHIELD Filed Jan. 15, 1965 INVENTOR.

NICHOLAS REINHARDT ATTORNEYS United States Patent 3,317,723 PROTECTIVE SHIELD Nicholas Reinhardt, Lexington, Mass., assignor to EG & G, line, a corporation of Massachusetts Filed Jan. 15, 1965, Ser. No. 425,695 1 Claim. (Cl. 240-47) ABSTRACT OF THE DISCLOSURE A protective shield assembly having a hollow cylindrical sleeve encompassing a cylindrical spring member that has a plurality of overlapping paddle-shaped arms that contact the interior surface of the sleeve and the exterior surface of the cylindrical object being protected.

This invention relates to protective devices and more particularly to shields for protecting objects or portions thereof from the damaging effects of attacking elements.

Although this invention is primarily related to shielding sources of illumination, it has far greater utility since it can shield any number of different objects from such environmental dangers as heat, light, infra-red, ultra-violet, alpha, beta, gamma, or x-radiations, miscroscopic or macroscopic particles or the like. In fact, any object that can be protected by a shield disposed about but spaced from it, may benefit from this invention. With a realization that this greater scope of utility is present, this invention, for simplicity, shall be described in its preferred embodiment as a protective shield for a light source.

Light sources have long been used with reflectors to increase the intensity of the light output in a given direction. In most cases, the source is so disposed in the reflector that some light and heat are unavoidably reflected back onto the light source itself.

In the case of high-power, very intense lights, the heat generated by the reflected light can cause considerable damage to the source. The heat so generated, when added to the internal heat produced by the lamp, is particularly injurious to electric-discharge flash lamps. The instantaneous power emitted during the flash is sufficient to melt, vaporize, or shatter objects, even though the average power (the instantaneous power divided by the time between flashes) is not harmful in any way. Normally, the most vulnerable point therein is the end seal where the transparent envelope is hermetically sealed to a metallic end cap. The great heat so attacks the end seals that the expected life of the flash lamp is reduced by as much as 75% and more. Occasionally, complete failure occurs after a single shot.

This problem resolved itself into an election between two undesirable operating conditions, short life for highintensity flashing or long life at reduced output. To avoid this dilemma and to attain greater light output without destroying the end seals, the prior art taught a number of proposed solutions to the problem. One such solution consists of pumping air or water through the system to dissipate the excessive heat. This solution required additional expensive and cumbersome equipment. Where space and cost were important considerations, this solution was impractical. A simple solution was proposed in the form of special tape applied over the end seals to reflect heat and to degrade the instantaneous heat pulse into a longer-duration lower-temperature pulse. (Same total energy but spread out in time at a lower temperature which would not harm the seal.) This proved unsatisfactory because the heat soon spoiled the adhesive and the tape fell off. The use of ceramic adhesive pastes was likewise unsatisfactory. The tape was also subject to carbonizing and burning. Still another solution was to machine a deep housing in the reflector to effect multiple 3,317,723 Patented May 2, 1967 reflections before the light was projected back in the direction of the flashlamp. Such a housing was expensive to machine. It was heavy and awkward to mount in equipment particularly where space was at a premium.

Covers and shields were proposed to fit over the end seals and shield them from the damaging heat. At the desired small overall diameters, which precluded the use of set screws or other conventional fastenings, poor mechanical grip to hold these units in place was their major disadvantage. Multiple reflections permitted the light to enter under the covers and strike the seals, thus, reducing their effectiveness. Stufling of the space between shields and seal with steel or copper wool aided in degrading the heat pulse but it was clumsy and did little to improve the mechanical grip. Furthermore, it was subject to working loose and rusting. Spring-wrap covers proved subject to loss of spring tension when exposed to the intense heat.

It is, therefore, an object of this invention to provide a protective shield assembly that may be interposed between the object to be protected and the potentially damaging elements without the aforementioned disadvantages.

Another object of this invention is to provide a heat and light shield for the end seals of light sources.

A further object is to provide a shield having a diameter only slightly in excess of the end seal to permit substantially universal use.

Still another object is to provide a novel spring for securely maintaining a protective shield in position about but spaced from the object to be protected.

Still a further object is to provide simple and economical shields which can easily be mounted and dismounted.

Other and further objects of this invention will be hereinafter pointed out in the following description and in the appended claims. In summary, this invention utilizes a hollow cylindrical light and heat shielding member which is disposed about and spaced from the end seals of a high-intensity light source, and a spring or resilient member, disposed between the member and the end seal for holding the member in position spaced from the light source, the leaves of which spring also constitute a baflie for absorbing and dispersing potentially damaging radiant energy.

Although the entire device may be made in the form of a single piece, it is preferable to use two separate pieces, a shielding member and a spring. In this way the member can shield the direct heat pulses while the spring can serve to degrade reflected heat and also maintain a good mechanical grip. It also improves the isolation between shield and end seal, allowing the heat pulse to be completely degraded to the average power level by the time it reaches the seal.

This invention will be better understood by reference to the following description considered in conjunction with the attached drawings of which:

FIGURE 1 is an exploded view of the elements of the applicants invention together with a portion of the light source to be protected;

FIGURE 2A is a sectional view of the protective shield assembly on the light source shown in FIGURE 1; FIG- URE 2B is a sectional view taken along the line AA of FIGURE 2A and looking in the direction of the arrows; FIGURE 2C is a perspective sectional view of the assembled shield;

FIGURE 3A is a plan view of a member of the shield assembly taken during fabrication thereof and FIGURE 3B is a perspective view of the completely fabricated member; and

FIGURE 4 is a sectional view of the other member of the protective shield assembly.

Referring first to FIGURE 1, there is shown a portion of a light source 10, such as, for example, a type FX-47 flashtube manufactured by the applicants assignee, E. G. & 6., Inc., Bedford, Massachusetts. Flashtube has an end cap 12 hermetically sealed to the lighttransmitting envelope 11, which may be glass, quartz or the like. Terminal connector 14 is attached to end cap 12 to pass electrical energy to the flashtube 10. The seal may be effected by any of the well-known glass-to-metal sealing means such as the solder seals taught in United States Letters Patent No. 2,756,361, issued on July 24, 1956, to Kenneth J. Germeshausen. Spaced from flashtube 10 in the exploded view of FIGURE 1 is a spring 16 which may be slipped over the flashtube end cap 12. Sleeve 15 may then be afiixed by sliding it over spring 16 with a slight rotary motion to suppress extension arms 17. When spring 16 and sleeve 15 are assembled in this simple and easy manner, the end seal of flashtube 10 is protected from the damaging effect of high-intensity pulses of heat and light.

FIGURES 2A, 2B and show the exploded parts of FIGURE 1 assembled on flashtube 10 to protect it. Disposed about end cap 12 of flashtube 10 is the hollow cylindrical sleeve 15 which is securely held in position by spring 16 whose extension arms 17 extend under the right hand edge of sleeve 15. In so doing, sleeve 15 is securely held in position over end cap 12 and spaced therefrom.

The shape and function of spring 16 will more easily by understood by referring to FIGURES 3A and 3B. In FIGURE 3A, spring 16 is shown as it would appear after it had been chemically etched from spring stock as taught in the applicants copending application Ser. No. 273,819, filed on Apr. 18, 1963, entitled, High Speed Chemical Machining, and now abandoned. Other types of metal forming may also be used, such as die stamping and the like. Spring 16 may be made from any of the materials normally used for springs, such as, for example, high tensile strength steel. .Spring 16 is formed so that there are a plurality of extension arms 17, which are directed outwardly from a central hub 18 which has an opening 19 concentric therein. Preferably each extension arm 17 has a broad paddle-like tip 20 which is wider than the extension arm itself. Note, that these paddle tips 20 are so formed that one edge of each extension arm 17 is straight while the other side has a step 21 which leads to the greater width at the paddle tip 20. The purpose of these paddle tips 20 is to provide a means for holding sleeve 15 in position about but spaced from the end seal of flashtube 10. A further purpose is to provide overlap or shingling" of the arms about the circumference of the flashtube to provide bafiling for heat and light. Spring 16 is shown with twelve extension arms 17 but more or less arms may be used. A minimum of three extension arms 17 is necessary to enable it to hold sleeve 15 securely in position.

Preferably, the number of arms 17 is chosen so that their paddle tips 20 are arranged in an overlapping relationship. In this way, the arms 17 intercept any radiant energy which may enter beneath sleeve 15. The overlap also provides a fulcrum for deflecting the paddle tips 20, one over the next which insures great frictional force against the inside of the sleeve 157and the outside of the flashtube 10. The maximum number of arms 17 is governed by considerations of strength and ruggedness of the spring itself.

FIGURE 3B shows spring 16 formed in the manner in which it may be employed in the applicants invention. Each extension arm 17 is bent at right angles to the central hub 18 so that arms 17 extend substantially parallel to the axis of flashtube 10 when mounted in position as shown in FIGURE 2C. The paddle-tips 20 are deflected cross-wise to their length in a turbine-like fashion. It is preferable to partially rotate each extension arm 17 in a direction such that the step 21 is on the outside and the straight side is on the inside as shown in FIG- URE 3B. This is preferred because it facilitates removal of the light shield as will be more fully discussed hereinafter.

When mounted in position, opening 19 in central hub 18 of spring 16 will pass over flashtube terminal connector 14, thereby placing hub 18 against flashtube end cap 12 with extension arms 17 extending over end cap 12 and resting against the envelope wall 11.

To increase its heat absorbing qualities and to assist in transferring degrading and dissipating heat from the flashtube end seal, spring 16 or portions thereof may be oxidized or painted to a dark or black color. By so doing, heat from the flashtube and in the spacing between the flashtube 10 and the sleeve 15 is absorbed by the spring and conducted to the sleeve where it is dissipated in the surrounding atmosphere.

The sleeve 15 is shown in FIGURE 4 as a hollow metal cylinder of, for example, copper, aluminum or other suitable material. For convenience sleeve 15 may be cut from tubing of the particular material selected, and, for economy, from a normally available commercial size. It is preferable to leave at one end of the sleeve, the natural burr produced by cutting the tube. This burr, shown as 13 in FIGURE 4, provides a smaller diameter at one end which readily serves as a stop against the hub 18 of spring 16 when these two parts are assembled, as shown in FIGURE 2. To facilitate assembly and disassembly, the opposite end of sleeve 15 should be machined smooth with no reduction of its inside diameter. By so doing, sleeve 15 easily slides over spring 16 and axially projecting arms 17 until the leading end of sleeve 15 rides up over the paddle tips 20, at which point the paddle tips 219 are deflected strongly, each over the next, in a shingled fashion, the edge of one serving as the fulcrum for deflection of the next. Some of this deflection is communicated along arms 17 toward the hub 18, the resulting twist of arms 17 serving to increase the effective diameter of the spring 16 so that in addition to the holding force exerted by the deflected paddle tips 20, a holding force is also exerted by the twisted arms in the vicinity of the end cap 12, thus holding shield 15 securely and concentrically at a minimum of two places along its axis. (All of the foregoing may be advantageously accomplished in a space between shield 15 and flashtube 10 which is only slightly greater than twice the spring-stock thickness in the region between shield 15 and envelope -11, or slightly greater than a single thickness between shield 15 and end cap 12.)

After paddle tips 20 and arms 17 have been deflected by the leading edge of shield 15, further advancement of the shield is easily made by slightly rotating shield 15 in the direction of deflections of the paddle tips 20. Advancement is continued until burr end 13 of shield 15 comes to a stop against hub 18, thus defining the preferred position of the shield 15. In the absence of a rotary force suflicient to depress paddle tips 20, the shield 15 will be found to be effectively locked in place by the outward edges of paddle tips 20 and arms 17, the inward edges likewise holding fast to the body and end cap of flashtube 10.-

The inside diameter of the sleeve 15 is in excess of the outside diameter of the flashtube 10 and the end cap 12 in order to provide space for the spring and thermal isolation therebetween. The outer surface of sleeve 15 should be polished in any of the well-known methods of polishing metal so that'it will reflect a high percentage of the light and heat incident thereupon.

It has been pointed out above that it is preferable to rotate extension arms 17 so that step 21 is on the outside to facilitate removal of the spring 16 and sleeve 15 from the flashtube 10. If, however, the use of the protective shield indicates a permanent assembly of the shield'on the flashtube is desired, then arms 17 should be rotated so that step '21 is on the inside edge of arms 17. In

this case, the step 21 engages end cap 12 and serves as a secondary fulcrum causing the leading edge of the paddle tip to bite into shield 15 when removal is attempted, making removal essentially impossible.

In the preferred mode of employment, however, both assembly and disassembly are facilitated by rotating sleeve 15 in the direction of the deflections of the paddle tips 20. By so doing, the tips 20 are depressed and the sleeve 15 is easily mounted in position or removed. The paddle tips 20 act in the manner of an overrunning clutch or ratchet which permits free motion in one direction but holds rigidly when the turning stops. Advancement or retraction may be made during rotary motion in the free direction.

It should be noted that a heavy-duty embodiment of this shield assembly when mounted over terminal connector 14, provides an electrical connection to the fiashtube via connector 14. An electrical connection may be made in any well-known manner to the outer surface of sleeve 15. Current could flow through sleeve and spring 16 to connector 14. In this case, sleeve 15 and spring 16 must be made from an electrically conductive material.

As an example of my invention, the fiashlarnp may be of the type FX47 mentioned above, having an outside, diameter for the envelope in the vicinity of the end cap of 0.354 inch and an end cap whose outside diameter is 0.395 inch. Spring 16 shall have a diameter of 1.3 inches from the tips of opposite arms 17 as shown in FIGURE 3A. Twelve extension arms 17 are equally spaced about hub 18, which has a central opening 19 with a diameter of 0.285 inch. Flashtube terminal 14 has a diameter of 0.280 inch. The extension arms 17 may be 0.45 inch and the tips of the paddles 20 may be 0.125 inch wide. Using a sleeve 15 of copper cut from tubing having an outside diameter of 0.5 inch and an inside diameter of approximately 0.43 inch, the sleeve length may be W of an inch, more or less. The length being governed primarily by the position of the end seal, the distance of the sleeve may extend therefrom without seriously interfering with the light emitted from the fiashtube.

As pointed out above, the object to be protected need not be a fiashtube nor is it necessary that the object be protected from heat. Other examples are a thermometer, or other exposed sensitive recording instruments protected from wind blown dirt and sand; photographic film protected from gamma radiation; and other similar applications.

Although I have described my invention with a great degree of particularity, especially with respect to the pre ferred embodiment, the invention is not to be construed so narrowly. Other and further modifications will occur to those skilled in this art and all such are deemed to fall within the spirit and scope of this invention.

I claim:

A shield for protecting the seal between the envelope and end cap of a fiashtube comprising, in combination, a hollow cylindrical sleeve of sufiicient length to cover said seal and having an inside diameter greater than the diameter of the end cap; and a spring having a plurality of overlapping paddle-shaped extension arms each having a greater terminal width than initial Width, parallel to the fiashtube and the sleeve, and disposed in the space therebetween, said arms being axially displaced a predetermined angle to exert a force against the sleeve and the fiashtube.

References Cited by the Examiner UNITED STATES PATENTS 1,042,979 10/1912 Seessle 240-138 2,176,657 2/1937 Finch 339112 2,551,710 5/1951 Slaughter 24051.11 2,677,755 6/1952 Moore 240-47 3,097,033 2/1959 Felts 339258 NORTON ANSHER, Primary Examiner.

W. M. FRYE, Assistant Examiner. 

